Pump



March 23, 1948. u. 1.. HOPPER rumr Filed Oct. 12, 1944 INVENTOR- Drv/yhf L. flop 0e)? Patented Mar. 23; 1948 PUMP Dwight L. Hopper, Wilkinsburg, Pa., assignor, by

v mesne assignments,

America, as represen the United States of ted by the United States Atomic Energy Commission Application October 12, 1944, Serial No. 558,355 6 Claims- (Cl. 230-101) My invention relates to a pump and, particularly, to a construction for improving the operating characteristics of a multiple stage diffusion pump.

In the operation of multiple stage diffusion pumps, it is customary to provide a boiler compartment for each pumping Stage of the pump. These boiler compartments have heretofore been separated by relatively thin metallic walls usually of spun material, Normally a pump has only one speed and an exhaust pressure dependent upon the air leak into the space being pumped. It has been customary to apply heat uniformly to all of the boiler compartments and when the rate of heating is changed, it is changed in all boiler compartments. However, the optimum operating conditions would be secured by applying different heat levels in the different boiler compartments.

According to my invention, this is accomplished by providing a separate heating element for each boiler compartment, the heating elements preferably being of the immersion type and the heat is prevented from transferring or migrating between the boiler compartments by using a heat insulating division between the boiler compartments.

I prefer to provide this heat insulating division by means of a double walled partition between the various boiler compartments and utilizing the double partition to provide a dead space which very efiectively prevents the. migration of heat between the boiler compartments so that they may be kept at difierent heat levels to secure the optimum operating characteristic of the pump. i

It is an object of my multistage diffusion pump crating characteristics.

A further object of my invention is to provide a pump boilerin which the boiler compartments may be maintained at difierent heat levels.

It is a further object of my invention to provide a multiple stage pump having different vapor pressures at the various pumping stages.

Other objects and advantages of my invention will be apparent from the following detailed description taken in conjunction with the accompanying drawing, in which:

Figure 1 is a sectional elevation of a pump embodying my invention; and

Fig. 2 is a similar view of a preferred embodiment of my invention. i

In the exemplary embodiment of the pump according to Fig. 1, a multiple stage pump i is invention to provide 9.

having improved opherein shown as a two stage pump for simplicity. However, it is obvious that any number of stages may be similarly constructed. Each stage 2, 3 of the pump I is provided with a vapor evolving or boiler chamber 4 5 and a conduit 6, 1 for conducting the vapor to a suitable diffusion nozzle 8, 9, the diffusion nozzles being surrounded by a cooled condensing surface l0. Each of the boiler chambers i, 5 is provided with a heater member I I, I2 preferably of the electrical immersion type which is preferably mounted below the surface of the liquid and supported on suitable insulating devices such as ceramic blocks l3. The leads l4, id for the heating elements H, 62 are brought out independently and the current through the heating elements ll, l2 may be adjusted by any suitable means (not shown).

The partition 25 between the boiler compartments 5, 5 is composed of a double walled device preferably constructed of two concentric spinnings it, ill welded or otherwise secured together to provide a hollow space l8 between the walls. In the modification according to Fig. l, the hollow space it will normally be filled with the vapor evolving material such as liquid oil, but in the confined space the liquid will be substantially dead or non-moving and, therefore, will transmit very little heat from one of the boiler compartments to the other. Passages it are provided for transferring the liquid, such as oil from the condensing space through the boiler compartments 1, 5, as may be desired.

In the type of pump as shown, the condensate is passed from the condensing chamber into the boiler compartment connected to the high pressure pumping stage 3 where the low volatiles will be distilled off and operate in the high pressure or discharge stage 3 of the pump l. The less volatile material will flow through the passage 99 into the low vacuum stage boiler 4 and will be utilized in the low vacuum or intake stage 2 of the pump. Preferably a dirt collecting barrier 2b is provided, usually in the form of a concentric ring secured to the bottom 22 of the outside boiler compartments to prevent dirt from being drawn into the boiler compartments associated with the low pressure pumping stage.

In the preferred embodiment according to Fig. 2, the double walled partition 25 is sealed at each end providing an annular space filled with relatively motionless air which is even a better heat insulator than the oil-filled wall. The fluid passage it between the various boiler compartments is preferably constructed by means of grooves or channels in the base plate 22 of the boiler and extending under the i the low boiling double walled partition 25.

This type of oil channel presents a relatively long passage so that there will be very little tendency for the heat to transfer between the boiler compartments through the interconnecting channels i9.

4 In the operation of the present embodiment elements II, It of the various compartments 4, 5

pump according to the will be adjusted to provide the optimum operating ressures for the various nozzles 8, 8 and the condensate from the nozzles 8, 9 will be returned to the vaporizing chamber 5 associated with the output or high pressure side 801' the pump where material will be vaporized and delivered to the nozzle 9 of the high pressure stage 3 while the higher boiling materials will be vaporized in the boiler compartments 4 associated with the low vacuum or intake side 2 of the pump 1. The double boiler compartments substantially heat insulates the two vaporizing chambers 4, 5 from each other so that various heat levels may be maintained in either of the. boiler compartments 4 or 5 without disturbing the heat level maintained in the adjacent compartments.

While for simplicity of illustration, I have shown and described preferred modifications of my invention it will beapparent to those skilled in the art that changes and modifications can be made therein without departing from the true spirit of my invention or the scope of the appended claims.

I claim as my invention:

of my invention, the heating 4. A difiusion pump comprising plurality of I pumping stages, a boiler compartment for each pumping stage, means for heating the boiler compartments to different temperature levels and means for substantially thermally insulating the boiler compartments from each other.

5. A diffusion pump comprising a plurality of pumping stages, a boiler compartment for each pumping stage, means for heating the boiler compartments to difl'erenttemperature levels, and a double walled portion between the boiler compartments to prevent heat interchange therebetween.

pump comprising a p urality of serially operating pumping stages, a vaporizing chamber for each pumping stage, individual heat- 1. A multistage vapor pump comprising a plurality of pumping stages, a boiler compartment for each pumping stage, heating means for each boiler compartment, and a double walled heat barrier between the boiler compartments.

- 2. A vapor pump comprising a plurality of serially operating pumping jets, a vaporizing compartment for each pumping jet, heating means mg means for each vaporizing chamber, a liquid passage between said vaporizing chamber and a dirt trap associated with said passage, and a thermal barrier between the vaporizing chambers. DWIGHT L. HOPPER.

a pearances crran UNITED STATES PATENTS Number Name Date 2,153,189 Hickman. Apr. 4, 1939 2,211,329 Hickman ing. 13, 1940 

